What Exactly Are Rainwater and Graywater?

Before we get too far into this, let’s define the two main types of water you can reuse from your building. The first is rainwater, and this is any type of precipitation that is on your roof surface in a large enough amount that it can be collected and reused. This could be rain, melting snow, sleet, etc. Reusing rainwater is a great way to save money on non-drinking applications in which the water needs to be purer than graywater.

The second type of water for collection is graywater, which is water that was drained from baths, showers, washing machines, and sinks; basically any type of water used within the building excluding toilet water. This water is not a benign product, as it may contain bacteria and other pathogens, and is therefore only to be used for irrigation and other non-drinking applications.

Benefits of Reusing Water

There are benefits both to you as a building owner or manager and to your municipal water providers from collecting and reusing water from your building.

First of all, this reduces the burden on your municipality and may offer financial savings to them. While only one building won’t change much, if many buildings start reusing rainwater and graywater and really start to make a dent in the system, you may see financial savings from the municipality passed on to you and other buildings.

When capturing rainwater, you can see the benefit of free water that can be used in many applications including evaporative coolers, washing of company vehicles and facilities, indoor and outdoor plant watering, livestock watering if applicable, lawn care, toilet flushing, and many other applications. If you were to stop paying for your water usage in those applications alone, you would see significant savings on your water bill each month.

Hazards to Avoid when Capturing and Reusing Rainwater and Graywater

Reusing graywater may cause negative repercussions on your municipal water provider, as it reduces the amount of water flow in the sewer systems. This reduced water may result in insufficient flow to carry waste to the sewer for treatment. Much like most other concepts regarding the capture and reuse of water, this is not a problem if only one or two buildings are reusing graywater, but if reuse becomes more prevalent, this problem will also become more likely to occur.

This is an example of a first-flush system that doesn’t capture the first few gallons

When reusing rainwater, water quality can become a major concern. The first few gallons of water captured off the roof typically contains bird poop, dust, and other debris. This water must somehow be filtered or must not be captured. There are contraptions that are designed to let the first few gallons avoid capture, but that is simply more investment and more work on your part.

Another issue with reusing rainwater is the fact that in highly populated areas, most rainwater is polluted as it is falling from the sky and absorbs arsenic, mercury, and other impurities in the atmosphere. If you are considering capturing and reusing rainwater on your building, you will just need to be careful that you aren’t using it in drinking applications.

Conclusion

Capturing and reusing of rainwater and graywater can yield great dividends to you as a building owner or facility manager, but is not without its downfalls, pitfalls, and shortcomings. As with any other decision you must make regarding your building, simply ensure that you do your own personal research and that you are comfortable with the subject before making decisions. If you’d like to see more articles like this, subscribe to the newsletter on the right to have our newsletter delivered directly to your inbox!